Again, another study finds that taking supplements is not always best for health. Many studies find that eating foods with vitamin "X" is beneficial, but taking high dose supplements may be linked to health problems (here, here, and here). Now a new study finds that long-term high dose supplementation with vitamins B6 and B12 is associated with a 30 to 40% higher lung cancer risk in men (compared to men who didn't take these supplements). Smokers had the greatest increase in risk. But interestingly, long-term use use of vitamins B6, folate, and B12 was not associated with lung cancer risk among women.
Good food sources of vitamin B6 are: poultry, fish, organ meats, potatoes and other starchy vegetables, chickpeas, and fruit (but not citrus). Good food sources of B12 are: Beef liver, clams, fish, meat, poultry, eggs, milk, and other dairy products. Bottom line: if you take vitamin supplements (such as daily multi-vitamin supplements), take a "low-dose" one - one that aims for 100% of minimum daily requirements, but not mega-doses of vitamins. From Medical Xpress:
New research suggests long-term, high-dose supplementation with vitamins B6 and B12—long touted by the vitamin industry for increasing energy and improving metabolism—is associated with a two- to four-fold increased lung cancer risk in men relative to non-users.
Risk was further elevated in male smokers taking more than 20 mg of B6 or 55 micrograms of B12 a day for 10 years. Male smokers taking B6 at this dose were three times more likely to develop lung cancer. Male smokers taking B12 at such doses were approximately four times more likely to develop the disease compared to non-users..... This is the first prospective, observational study to look at the effects of long-term high-dose B6/B12 supplement use and lung cancer risk. These supplements have been broadly thought to reduce cancer risk.
For this study, Theodore Brasky, PhD, of the OSUCCC - James, and colleagues analyzed data from more than 77,000 patients participants in the VITamins And Lifestyle (VITAL) cohort study, a long-term prospective observational study designed to evaluate vitamin and other mineral supplements in relation to cancer risk. All participants were aged between 50 and 76 were recruited in the state of Washington between the years 2000 and 2002. Upon enrolling in the study, participants reported information to researchers about B-vitamin usage over the past 10 years. This included dosage information.
Brasky notes these findings relate to doses that are well above those from taking a multivitamin every day for 10 years. "These are doses that can only be obtained from taking high-dose B vitamin supplements, and these supplements are many times the U.S. Recommended Dietary Allowance," he said. Two additional studies are underway at The OSUCCC - James to further evaluate high dose, long-term B6 and B12 supplementation and lung cancer risk. [Original study.]